Projection exposure apparatus, cleaning and maintenance methods of a projection exposure apparatus, and device manufacturing method

Abstract

A projection exposure apparatus that exposes a substrate with a liquid interposed between a surface of the substrate and an optical element on the substrate side of a projection optical system; includes liquid supply and discharge mechanisms, which supply the liquid via a liquid supply tube as they recover the liquid via a liquid recovery tube, and an adhesion preventing mechanism that prevents an adhesion of impurities on member forming a flow path for the liquid.

What is claimed is: 
     
       1. A liquid immersion type projection exposure apparatus in which a space under an optical element is filled with a liquid, the liquid immersion type projection exposure apparatus comprising:
 a liquid supply system connected to a supply flow path, which supplies the liquid to the space via the supply flow path; 
 a liquid recovery system connected into a recovery flow path, which removes the liquid from the space to the recovery flow path; and 
 a cleaning system which performs a cleaning operation, the cleaning system having a flow meter which ascertains a liquid supply flow volume per unit time and a controller which controls the liquid supply system and the liquid recovery system such that (i) the liquid supply flow volume per unit time fluctuates, and (ii) the liquid in the space under the optical element covers only a portion of a surface of an object located under the optical element by supplying the liquid to the space via the liquid supply path and recovering the liquid from the space into the recovery flow path. 
 
     
     
       2. The projection exposure apparatus according to  claim 1 , wherein:
 the cleaning system has a flow meter, which ascertains a liquid recovery flow volume per unit time, and 
 the controller controls the liquid supply system and the liquid recovery system so that the liquid supply flow volume per unit time and the liquid recovery flow volume per unit time become linked and fluctuate. 
 
     
     
       3. The projection exposure apparatus according to  claim 1 , wherein the liquid supply flow volume per unit time fluctuates at an amplitude of 0.1% or more with respect to a time average value of the liquid supply flow volume. 
     
     
       4. The projection exposure apparatus according to  claim 1 , wherein the cleaning system performs the cleaning operation when exposure has stopped. 
     
     
       5. The projection exposure apparatus according to  claim 1 , wherein the optical element is a synthetic calcium fluoride monocrystal. 
     
     
       6. The projection exposure apparatus according to  claim 5 , wherein a surface of the optical element that contacts the liquid is coated with magnesium fluoride. 
     
     
       7. The projection exposure apparatus according to  claim 1 , wherein purified water or an aqueous solution in which salts are dissolved is used as the liquid. 
     
     
       8. The projection exposure apparatus according to  claim 1 , wherein the liquid supply flow path is cleaned during the cleaning operation. 
     
     
       9. The projection exposure apparatus according to  claim 1 , wherein the liquid recovery flow path is cleaned during the cleaning operation. 
     
     
       10. A device manufacturing method that uses the liquid immersion type projection exposure apparatus as recited in  claim 1 . 
     
     
       11. A cleaning method of a liquid immersion type projection exposure apparatus in which a space under an optical element is filled with a liquid while supplying the liquid to the space via a supply flow path and recovering the liquid from the space into a recovery flow path, the method comprising:
 placing an object under the optical element such that the space is located between the optical element and a surface of the object; and 
 performing a cleaning operation in which (i) the liquid supply flow volume per unit time fluctuates, and (ii) the liquid in the space under the optical element covers only a portion of the surface of the object placed under the optical element by supplying the liquid to the space via the liquid supply path and recovering the liquid from the space into the recovery flow path. 
 
     
     
       12. The cleaning method of the projection exposure apparatus according to  claim 11 , wherein the liquid supply flow per unit time fluctuates at an amplitude of 0.1% or more with respect to a time average value of the liquid supply flow volume. 
     
     
       13. A device manufacturing method that uses the cleaning method of a liquid immersion type projection exposure apparatus as recited in  claim 11 . 
     
     
       14. The cleaning method of the projection exposure apparatus according to  claim 11 , wherein the liquid recovery flow volume per unit time fluctuates during the cleaning operation. 
     
     
       15. The cleaning method of the projection exposure apparatus according to  claim 11 , wherein the liquid supply flow volume per unit time and the liquid recovery flow volume per unit time become linked and fluctuate during the cleaning operation.